changed type of userlist from vector to set
QSettings eingebunden
merge
client cleanup
Slot in main-function fuer logout-Funktion verbunden
merged
cleanup
added class ChatWin. For connecting Signals and Slots for Login and other Client Windows
Register and Login via Welcome-Window
Bugfix for Register via WelcomeWindow
Leave Chat implemented
Merge pull request #20 from sepm-depm/ServerMR

Server mr
remove wrong test - can't know which chats exist on remote
Bugfix regarding signature
Merge pull request #21 from sepm-depm/ChatManager

Chat manager
clarify comment
display error messages sent from server
Merge pull request #22 from sepm-depm/client-error-messages

display error messages sent from server

thanks :)
Merge branch 'ServerMR'
fix resource leak